Nonwoven fiber glass mats are conventionally produced by dispersing glass fibers in chemically treated water to form an aqueous slurry stock, depositing the slurry onto a foraminous forming belt, such as the chain or wire of a Fourdrinier machine, while the belt is moving through a fiber deposition zone, and drawing water from the slurry through the belt to cause a layer of fiber to remain on the belt. The slurry stock is brought to the moving belt in quantities correlated to the speed of the belt to produce a mat comprised of fibers which are oriented in a predetermined manner. For example, if the stock is introduced to the moving wire at a relatively slow rate compared to the speed of the wire, the fibers become oriented in the machine direction. If the stock is introduced at a relatively fast rate compared to the speed of the wire, the fibers are distributed on the wire in random orientation. While both directionally and randomly oriented mats are suited for various types of applications, it would be beneficial in some applications to have a mat which contains separate areas of different character.
U.S. Pat. No. 3,969,561 discloses an air-borne method of forming a nonwoven fibrous mat which involves the use of either impervious bars disposed over a forming screen or impervious areas incorporated into the screen. Fibers are thereby prevented from being deposited on the screen beneath the bars or in the impervious areas of the screen. The impervious bars or screen areas extend throughout the entire fiber deposition zone so that at no point does the stream of fibers encounter an area which is completely unblocked. The dimensions and spacing of the impervious bars or areas are such that fibers falling on them are able to bridge across to the unblocked areas. In that way a mat is formed continuously across the width of the screen, with the fibers in the portions of the mat corresponding to the adjacent blocked and unblocked areas of the screen being at right angles to each other. The method is disclosed in connection with the manufacture of decorative striped fabrics.
U.S. Pat. No. 4,070,235 discloses a method for making a nonwoven fibrous mat from an aqueous slurry by utilizing fluid impervious bars to block portions of a forming screen or by incorporating fluid impervious blocking means into the forming screen. Fibers of different lengths are used to obtain the desired bridging effect. The impervious bars or screen areas extend throughout the entire fiber deposition zone, as in the disclosure of U.S. Pat. No. 3,969,561. The product produced is similar to the product produced by the method of U.S. Pat. No. 3,969,561.
The mats produced by these methods are restricted in design to the configurations made possible by the method of production. It would be desirable to be able to produce nonwoven mats having different and more varied designs incorporated into the body of the mat. It would also be beneficial to be able to produce a mat which has areas of different physical properties so as to be especially suited for certain specific types of installations, making it possible to customize a mat depending on its intended use.